Right ventricular dysfunction developing late after congenital cardiac surgery is one of the most common causes of heart failure in adults with congenital heart disease. In tetra logy of Fallot (ToF), the most common cyanotic heart defect, initial repair in infancy involves an incision and patch in the RV outflow, including the pulmonary valve, which often results in late development of severe RV dilatation and dysfunction due to chronic pulmonary regurgitation and RV scarring/patch dilatation. Current surgical management of late RV dysfunction, consisting of pulmonary valve insertion and reduction of the RV outflow patch, reduces RV volume but does not result in a predictable improvement in RV function. A more radical procedure, which includes extensive removal of scar and outflow patch, is being evaluated in an NHLBI sponsored randomized prospective trial. However, there is no currently available method for predicting outcome after either procedure or what the optimal procedure is for a given pt., i.e. no clinically useful tools for determining patient-specific therapy. In this project, we propose to develop a computational modeling approach to determine the efficacy and suitability of the various reconstructive options to treat failing RV in ToF pts. We will use non-invasive cardiac magnetic resonance imaging (CMR) to provide patient-specific RV/LV morphology, deformation, and flow data for the construction and validation of computational models. 3D CMR-based RV/LV combination models will be constructed, which include fluid-structure interactions (RV/LV and RV patch), two-layer RV/LV structure, anisotropic material properties, fiber orientation, and active contraction to simulate blood flow, heart motion, and stress/strain distribution to evaluate the effect of different remodeling procedures on RV function, and to seek an optimal RV volume and patch design to improve post-operative RV function. Clinical imaging and hemodynamic data from an ongoing NHLBI-funded clinical trial will be used to build and validate the model. Our ultimate goal is to apply this methodology in patient- specific computer-aided cardiac surgery planning to reach optimal surgical procedure design and outcome in patients with RV dysfunction from congenital heart defects. A multidisciplinary group of experienced investigators in congenital cardiac surgery, cardiology and computational mathematics will conduct this project.